Fitness is all about being physically fit (who knew!) You will train for you ability to sustain low and high intensity cardio such as running, biking and rowing while also doing some calisthenics to get better at dips, pullups, pushups and chinups. You will also (after awhile) start encorporating free weights into your programs and also core work. This is about the reps, the endurance, the lung and heart conditioning required to sustain intense activities.
 

Rep/set types:
High reps, long duration cardio, timed workouts

You will love fitness if:
You want to look lean (low body fat)
You want to be physically fit
You want to be athletic
If you care more about what you can do than what you look like
 

It's not for you if:
You wan't large muscle size
funcitonality doesn't mean much to you
You dislike high reps
You want to be strong like an ox

Cardio makes your inner child cry